That news comes from researchers including Meliha Karsak, PhD, and Thomas Tuting, MD, of Germany's University of Bonn.

Marijuana's key compound, THC, is a type of chemical called a cannabinoid. The brain contains two types of cannabinoid receptors.

Karsak and colleagues studied mice born with or without cannabinoid receptors. The mice wore ear tags to identify them; those ear tags contained nickel.

The mice without cannabinoid receptors were particularly likely to have allergic skin reactions to the nickel in the ear tags.

The scientists reasoned that the mice's allergies may have been linked to their lack of cannabinoid receptors.

Karsak's team tested that theory in several experiments.

First, they turned off cannabinoid receptors in healthy mice. Those mice then became more likely to develop skin inflammation near their nickel ear tags.

Next, the researchers exposed other mice with cannabinoid receptors to a skin irritant. Some of the mice got THC shots after being exposed to the irritant. Others got a THC skin lotion before and after exposure to the irritant.

The THC shot and lotion both helped soothe the mice's inflamed skin.

"If we dabbed THC solution onto the animals' skin shortly before and after applying the allergen, a lot less swelling occurred than normal," Tuting says in a University of Bonn news release.

In the journal Science, the researchers write that their study "strongly suggests" that the body's cannabinoid system can help tame inflammation and that THC skin lotions have "promising potential" for treating skin allergies caused by contact with irritating chemicals.

However, the researchers didn't test the THC lotion on skin allergies in people.